The Famous Study That Made 'Decision Fatigue' a Household Term

This is the study that put 'decision fatigue' into everyday vocabulary. Researchers tracked more than 1,100 parole hearings by experienced Israeli judges over ten months, dividing each working day into sessions separated by food breaks. The pattern was striking and remarkably consistent: prisoners had roughly a 65 percent chance of a favourable ruling at the start of each session, a probability that fell steadily, sometimes to almost zero, by the session's end, then jumped straight back to 65 percent after the judges had rested and eaten. The authors' interpretation was that mental depletion pushed tired judges toward the easiest, lowest-effort decision, denying parole and preserving the status quo.

This became one of the most cited findings in behavioural science, and also one of the most contested, addressed separately in this hub because the scrutiny it later attracted is as instructive as the original finding. On its own terms, it's an observational study of a single professional context, judicial parole decisions, so it can't establish that the same pattern applies to ordinary daily choices. As later analyses would show, it also couldn't fully rule out that something other than fatigue was driving the pattern.